‘Species’ Begone? A Lesson in Pluralism and Pragmatism

Marc Ereshefsky

What is a prokaryote species? The problem in answering this question is not that there
is no answer but there are too many answers. There are multiple prokaryote species
concepts that highlight different groups of organisms. Furthermore, discordance due
to lateral gene transfer results in numerous candidates for prokaryote species. The
number of prokaryote species is only limited by which genes are taken as significant
for classification, which is not much of a limit. Consequently, we have ample evidence
that there is no unified prokaryote species category. Some have suggested that such
problems imply that the word ‘species’ should be eliminated from microbial discourse.
That suggestion is hasty and impractical. The word ‘species’ is ever-present in such
diverse areas as epidemiology, agriculture, and geochemistry and won’t disappear anytime
soon. Furthermore, there is no compelling practical reason to get rid of the term
‘species.’